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噪声椒盐噪点可以用中值滤波器消除，有条纹状的噪声可以用陷波滤波器，比较细致模糊的噪点可以用低通滤波器
卷积线性滤波器全通没有,"> 
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        <h1 class="title">视觉计算观后感</h1>
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            <span>三月 13, 2022</span>
            
  <ul class="post-tags-list" itemprop="keywords"><li class="post-tags-list-item"><a class="post-tags-list-link" href="/blog/tags/%E8%AE%A1%E7%AE%97%E6%9C%BA%E8%A7%86%E8%A7%89/" rel="tag">计算机视觉</a></li></ul>


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            <h1 id="数据"><a href="#数据" class="headerlink" title="数据"></a>数据</h1><h2 id="采样"><a href="#采样" class="headerlink" title="采样"></a>采样</h2><p>从样本数据提取数据，等距提取就是均匀采样，不等距就是非均匀采样。</p>
<h2 id="噪声"><a href="#噪声" class="headerlink" title="噪声"></a>噪声</h2><p>椒盐噪点可以用中值滤波器消除，有条纹状的噪声可以用陷波滤波器，比较细致模糊的噪点可以用低通滤波器</p>
<h1 id="卷积"><a href="#卷积" class="headerlink" title="卷积"></a>卷积</h1><h2 id="线性滤波器"><a href="#线性滤波器" class="headerlink" title="线性滤波器"></a>线性滤波器</h2><h3 id="全通"><a href="#全通" class="headerlink" title="全通"></a>全通</h3><p>没有消除和阻止任何一个频率。作用未知。</p>
<h3 id="低通"><a href="#低通" class="headerlink" title="低通"></a>低通</h3><p>使频率越来越宽，可以让图片变得模糊和达到消除噪点的作用</p>
<h4 id="盒式滤波器"><a href="#盒式滤波器" class="headerlink" title="盒式滤波器"></a>盒式滤波器</h4><p>使用全为1的卷积核。</p>
<h4 id="高斯滤波器"><a href="#高斯滤波器" class="headerlink" title="高斯滤波器"></a>高斯滤波器</h4><p>特定的权重，离像素点越远权重越小</p>
<p>下图为高斯函数的3维图示：</p>
<p><img src="https://pic4.zhimg.com/80/v2-d6af23aafa14caec06b3a1790b6d92e3_720w.jpg"></p>
<p>0.05 0.25 0.40 0.25 0.05权值</p>
<h4 id="降低频率采样"><a href="#降低频率采样" class="headerlink" title="降低频率采样"></a>降低频率采样</h4><p>n层：1 x 1</p>
<p>···</p>
<p>n-1层：pow(2,n-1) x pow(2,n-1)</p>
<p>n层：pow(2,n) x pow(2,n)</p>
<p>高斯金字塔</p>
<p>n-1层的一个网格对应相应的n层的4个网格</p>
<h4 id="卷积细节"><a href="#卷积细节" class="headerlink" title="卷积细节"></a>卷积细节</h4><ol>
<li>将滤波器与图像进行卷积时，要每个像素对齐非常重要，每个卷积的结果要单独保存，否则会影响之后的卷积结果</li>
<li>运算时先转化为浮点数再进行滤波最后滤波取整</li>
<li>如果颜色超过0，255设定最大值和最小值s</li>
</ol>
<h3 id="高通"><a href="#高通" class="headerlink" title="高通"></a>高通</h3><p>留下高频去除低频，能得到图形边缘特征。</p>
<p>如核为 -1&#x2F;3 2&#x2F;3 -1&#x2F;3的卷积核。</p>
<h3 id="带通"><a href="#带通" class="headerlink" title="带通"></a>带通</h3><p>指留下低频和高频之间的信号。</p>
<h2 id="非线性滤波器"><a href="#非线性滤波器" class="headerlink" title="非线性滤波器"></a>非线性滤波器</h2><h3 id="中值滤波器"><a href="#中值滤波器" class="headerlink" title="中值滤波器"></a>中值滤波器</h3><p>去核范围的中值代替像素，去椒盐噪点的，还可以制作腐蚀或膨胀效果。</p>
<h1 id="几何变换"><a href="#几何变换" class="headerlink" title="几何变换"></a>几何变换</h1><h2 id="平移旋转放缩"><a href="#平移旋转放缩" class="headerlink" title="平移旋转放缩"></a>平移旋转放缩</h2><p><a target="_blank" rel="noopener" href="https://learnopengl-cn.github.io/01%20Getting%20started/07%20Transformations/">opengl</a>里面有 就不看了</p>
<h2 id="透视变换"><a href="#透视变换" class="headerlink" title="透视变换"></a>透视变换</h2><p>裁剪距阵的推导<br><img src="https://img-blog.csdnimg.cn/c190892dadc14693a1333ea6a36d8882.png?x-oss-process=image/watermark,type_d3F5LXplbmhlaQ,shadow_50,text_Q1NETiBAUEMgRXJyb3I=,size_20,color_FFFFFF,t_70,g_se,x_16" alt="请添加图片描述"><br>取用这个坐标系，所以w是0 0 -1 0<br>$$<br>∠theta&#x3D;fov&#x2F;2 ,A&#x3D;  N * tan (theta),B&#x3D;  F * tan (theta) \ A’&#x3D;N&#x3D;ACot(theta),B’&#x3D;F&#x3D;BCot(theta)<br>$$<br>所以Y轴是 0 cot(theta) 0 0。<br><img src="https://img-blog.csdnimg.cn/882a9c5831444a61ab5f8edf4f74d502.png?x-oss-process=image/watermark,type_d3F5LXplbmhlaQ,shadow_50,text_Q1NETiBAUEMgRXJyb3I=,size_20,color_FFFFFF,t_70,g_se,x_16" alt="请添加图片描述"><br>ASP是宽高比</p>
<figure class="highlight markdown"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">$$</span><br><span class="line">C=A<span class="emphasis">*ASP \\</span></span><br><span class="line"><span class="emphasis">D=B*</span>ASP \\</span><br><span class="line">C&#x27;=N=C<span class="emphasis">*Cot(theta) / ASP \\ </span></span><br><span class="line"><span class="emphasis">D&#x27;=F=D*</span>Cot(theta) / ASP</span><br><span class="line">$$</span><br></pre></td></tr></table></figure>

<p>所以x是&#x3D;Cot(theta)&#x2F;ASP 0  0 0。</p>
<p>假设矩阵是线性的<br>$$<br>f(-N)&#x3D;-N,f(-F)&#x3D;F代入方程y&#x3D;sx+o<br>$$<br>解方程组<br>$$<br>s&#x3D;(f+n)&#x2F;(n-f),o&#x3D;2fn&#x2F;(n-f)<br>$$<br>z是0 0 s o；</p>
<p>得透视矩阵如下</p>
<p> <img src="https://img-blog.csdnimg.cn/fc31696d20124d45ae3f5291895b5e7b.png?x-oss-process=image/watermark,type_d3F5LXplbmhlaQ,shadow_50,text_Q1NETiBAUEMgRXJyb3I=,size_16,color_FFFFFF,t_70,g_se,x_16" alt="在这里插入图片描述"></p>

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			<ol class="toc"><li class="toc-item toc-level-1"><a class="toc-link" href="#%E6%95%B0%E6%8D%AE"><span class="toc-number">1.</span> <span class="toc-text">数据</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#%E9%87%87%E6%A0%B7"><span class="toc-number">1.1.</span> <span class="toc-text">采样</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E5%99%AA%E5%A3%B0"><span class="toc-number">1.2.</span> <span class="toc-text">噪声</span></a></li></ol></li><li class="toc-item toc-level-1"><a class="toc-link" href="#%E5%8D%B7%E7%A7%AF"><span class="toc-number">2.</span> <span class="toc-text">卷积</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#%E7%BA%BF%E6%80%A7%E6%BB%A4%E6%B3%A2%E5%99%A8"><span class="toc-number">2.1.</span> <span class="toc-text">线性滤波器</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%85%A8%E9%80%9A"><span class="toc-number">2.1.1.</span> <span class="toc-text">全通</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E4%BD%8E%E9%80%9A"><span class="toc-number">2.1.2.</span> <span class="toc-text">低通</span></a><ol class="toc-child"><li class="toc-item toc-level-4"><a class="toc-link" href="#%E7%9B%92%E5%BC%8F%E6%BB%A4%E6%B3%A2%E5%99%A8"><span class="toc-number">2.1.2.1.</span> <span class="toc-text">盒式滤波器</span></a></li><li class="toc-item toc-level-4"><a class="toc-link" href="#%E9%AB%98%E6%96%AF%E6%BB%A4%E6%B3%A2%E5%99%A8"><span class="toc-number">2.1.2.2.</span> <span class="toc-text">高斯滤波器</span></a></li><li class="toc-item toc-level-4"><a class="toc-link" href="#%E9%99%8D%E4%BD%8E%E9%A2%91%E7%8E%87%E9%87%87%E6%A0%B7"><span class="toc-number">2.1.2.3.</span> <span class="toc-text">降低频率采样</span></a></li><li class="toc-item toc-level-4"><a class="toc-link" href="#%E5%8D%B7%E7%A7%AF%E7%BB%86%E8%8A%82"><span class="toc-number">2.1.2.4.</span> <span class="toc-text">卷积细节</span></a></li></ol></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E9%AB%98%E9%80%9A"><span class="toc-number">2.1.3.</span> <span class="toc-text">高通</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%B8%A6%E9%80%9A"><span class="toc-number">2.1.4.</span> <span class="toc-text">带通</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E9%9D%9E%E7%BA%BF%E6%80%A7%E6%BB%A4%E6%B3%A2%E5%99%A8"><span class="toc-number">2.2.</span> <span class="toc-text">非线性滤波器</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E4%B8%AD%E5%80%BC%E6%BB%A4%E6%B3%A2%E5%99%A8"><span class="toc-number">2.2.1.</span> <span class="toc-text">中值滤波器</span></a></li></ol></li></ol></li><li class="toc-item toc-level-1"><a class="toc-link" href="#%E5%87%A0%E4%BD%95%E5%8F%98%E6%8D%A2"><span class="toc-number">3.</span> <span class="toc-text">几何变换</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#%E5%B9%B3%E7%A7%BB%E6%97%8B%E8%BD%AC%E6%94%BE%E7%BC%A9"><span class="toc-number">3.1.</span> <span class="toc-text">平移旋转放缩</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E9%80%8F%E8%A7%86%E5%8F%98%E6%8D%A2"><span class="toc-number">3.2.</span> <span class="toc-text">透视变换</span></a></li></ol></li></ol>	
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